But there are also significant flaws. Baker's slick journalistic style grates after a while - especially when we are forced to hear about him supping yet another coffee in a cafe as he waits for his next interviewee. And maybe it's because I'm a maths nerd, but I hoped for more detail about the maths involved. Baker's mathematical descriptions are often superficial, and indeed he seems to regard the maths as little more than magic. His numerati come across as sorcerers armed with mysterious, secret knowledge, not as scientists with tools that can be rationally analysed. This has the effect of making them seem more sinister than they are.

The book becomes more interesting when Baker turns his attention to the political implications of the numerati's activities. There are clear issues of civil liberties at stake, as well as of consent. Most of us have no idea how much of our lives are being tracked. If we did, we would probably be horrified. At the same time, it is hard to deny that the numerati do much that is good. Baker's analysis is pretty balanced, and he spells out why we should be grateful to the numerati, as well as concerned in some areas.

Increasingly, for example, the numerati use their skills to monitor health care; homes for the elderly are being wired with technology that can record fluctuations in weight or a decrease in mobility, triggering a hasty visit from a doctor. If you're joining a dating agency, you want to exploit the skills of mathematicians to find the perfect partner. And, as Baker points out in his chapter on the use of the numerati by pollsters, anything that helps politicians target individuals on issues that they care about, rather than simply trotting out bland platitudes, is a good thing.